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RedHat 9 (Linux i386) - man page for agetty (redhat section 8)

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AGETTY(8)										AGETTY(8)

       agetty - alternative Linux getty

       agetty [-ihLmnw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host]
       port baud_rate,...  [term]
       agetty [-ihLmnw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host]
       baud_rate,...  port [term]

       agetty  opens  a tty port, prompts for a login name and invokes the /bin/login command. It
       is normally invoked by init(8).

       agetty has several non-standard features that are useful for hard-wired	and  for  dial-in

       o      Adapts  the  tty settings to parity bits and to erase, kill, end-of-line and upper-
	      case characters when it reads a login name.  The program can handle  7-bit  charac-
	      ters with even, odd, none or space parity, and 8-bit characters with no parity. The
	      following special characters are recognized: @ and Control-U  (kill);  #,  DEL  and
	      back space (erase); carriage return and line feed (end of line).

       o      Optionally   deduces   the   baud  rate  from  the  CONNECT  messages  produced  by
	      Hayes(tm)-compatible modems.

       o      Optionally does not hang up when it is given an already  opened  line  (useful  for
	      call-back applications).

       o      Optionally does not display the contents of the /etc/issue file.

       o      Optionally displays an alternative issue file instead of /etc/issue.

       o      Optionally does not ask for a login name.

       o      Optionally invokes a non-standard login program instead of /bin/login.

       o      Optionally turns on hard-ware flow control

       o      Optionally forces the line to be local with no need for carrier detect.

       This program does not use the /etc/gettydefs (System V) or /etc/gettytab (SunOS 4) files.

       port   A  path  name relative to the /dev directory. If a "-" is specified, agetty assumes
	      that its standard input is already connected to a tty port and that a connection to
	      a remote user has already been established.

	      Under System V, a "-" port argument should be preceded by a "--".

	      A comma-separated list of one or more baud rates. Each time agetty receives a BREAK
	      character it advances through the list, which is treated as if it were circular.

	      Baud rates should be specified in descending order,  so  that  the  null	character
	      (Ctrl-@) can also be used for baud rate switching.

       term   The  value  to  be  used for the TERM environment variable. This overrides whatever
	      init(8) may have set, and is inherited by login and the shell.

       -h     Enable hardware (RTS/CTS) flow control. It is left up to the application to disable
	      software (XON/XOFF) flow protocol where appropriate.

       -i     Do  not  display	the  contents  of  /etc/issue (or other) before writing the login
	      prompt. Terminals or communications hardware may	become	confused  when	receiving
	      lots  of	text at the wrong baud rate; dial-up scripts may fail if the login prompt
	      is preceded by too much text.

       -f issue_file
	      Display the contents of issue_file instead of /etc/issue.  This allows custom  mes-
	      sages  to  be  displayed	on different terminals.  The -i option will override this

       -I initstring
	      Set an initial string to be sent to the tty or modem before sending anything  else.
	      This  may  be  used to initialize a modem.  Non printable characters may be sent by
	      writing their octal code preceded by a backslash (\). For example to send  a  line-
	      feed character (ASCII 10, octal 012) write \012.

       -l login_program
	      Invoke the specified login_program instead of /bin/login.  This allows the use of a
	      non-standard login program (for example, one that asks for a  dial-up  password  or
	      that uses a different password file).

       -H login_host
	      Write  the  specified  login_host  into  the utmp file. (Normally, no login host is
	      given, since agetty is used for local hardwired connections and consoles.  However,
	      this option can be useful for identifying terminal concentrators and the like.

       -m     Try  to extract the baud rate the CONNECT status message produced by Hayes(tm)-com-
	      patible modems. These status  messages  are  of  the  form:  "<junk><speed><junk>".
	      agetty  assumes that the modem emits its status message at the same speed as speci-
	      fied with (the first) baud_rate value on the command line.

	      Since the -m feature may fail on heavily-loaded systems, you  still  should  enable
	      BREAK processing by enumerating all expected baud rates on the command line.

       -n     Do  not  prompt  the  user for a login name. This can be used in connection with -l
	      option to invoke a non-standard login process such as a BBS system. Note that  with
	      the  -n  option,	agetty gets no input from user who logs in and therefore won't be
	      able to figure out parity, character size, and newline processing  of  the  connec-
	      tion.  It defaults to space parity, 7 bit characters, and ASCII CR (13) end-of-line
	      character.  Beware that the program that agetty starts (usually /bin/login) is  run
	      as root.

       -t timeout
	      Terminate  if no user name could be read within timeout seconds. This option should
	      probably not be used with hard-wired lines.

       -L     Force the line to be a local line with no need for carrier detect. This can be use-
	      ful  when  you  have a locally attached terminal where the serial line does not set
	      the carrier detect signal.

       -w     Wait for the user or the modem to send a carriage-return or  a  linefeed	character
	      before  sending the /etc/issue (or other) file and the login prompt. Very useful in
	      connection with the -I option.

       This section shows examples for the process field of an entry in  the  /etc/inittab  file.
       You'll  have  to prepend appropriate values for the other fields.  See inittab(5) for more

       For a hard-wired line or a console tty:
	    /sbin/agetty 9600 ttyS1

       For a directly connected terminal without proper carriage detect wiring: (try this if your
       terminal just sleeps instead of giving you a password: prompt.)
	    /sbin/agetty -L 9600 ttyS1 vt100

       For a old style dial-in line with a 9600/2400/1200 baud modem:
	    /sbin/agetty -mt60 ttyS1 9600,2400,1200

       For  a  Hayes  modem  with  a fixed 115200 bps interface to the machine: (the example init
       string turns off modem echo and result codes, makes modem/computer DCD  track  modem/modem
       DCD, makes a DTR drop cause a dis-connection and turn on auto-answer after 1 ring.)
	    /sbin/agetty -w -I 'ATE0Q1&D2&C1S0=1\015' 115200 ttyS1

       The  issue-file (/etc/issue or the file set with the -f option) may contain certain escape
       codes to display the system name, date and time etc. All escape codes consist of  a  back-
       slash (\) immediately followed by one of the letters explained below.

       b      Insert the baudrate of the current line.

       d      Insert the current date.

       s      Insert the system name, the name of the operating system.

       l      Insert the name of the current tty line.

       m      Insert the architecture identifier of the machine, eg. i486

       n      Insert the nodename of the machine, also known as the hostname.

       o      Insert the domainname of the machine.

       r      Insert the release number of the OS, eg. 1.1.9.

       t      Insert the current time.

       u      Insert the number of current users logged in.

       U      Insert  the string "1 user" or "<n> users" where <n> is the number of current users
	      logged in.

       v      Insert the version of the OS, eg. the build-date etc.

       Example: On my system, the following /etc/issue file:

	      This is \n.\o (\s \m \r) \t

       displays as

	      This is thingol.orcan.dk (Linux i386 1.1.9) 18:29:30

       /var/run/utmp, the system status file.
       /etc/issue, printed before the login prompt.
       /dev/console, problem reports (if syslog(3) is not used).
       /etc/inittab, init(8) configuration file.

       The baud-rate detection feature (the -m option) requires that  agetty  be  scheduled  soon
       enough  after  completion  of  a  dial-in call (within 30 ms with modems that talk at 2400
       baud). For robustness, always use the -m option in combination with a multiple  baud  rate
       command-line argument, so that BREAK processing is enabled.

       The  text  in  the  /etc/issue file (or other) and the login prompt are always output with
       7-bit characters and space parity.

       The baud-rate detection feature (the -m option) requires that the modem emits  its  status
       message after raising the DCD line.

       Depending  on  how  the program was configured, all diagnostics are written to the console
       device or reported via the syslog(3) facility.  Error messages are produced  if	the  port
       argument  does  not  specify  a terminal device; if there is no utmp entry for the current
       process (System V only); and so on.

       W.Z. Venema <wietse@wzv.win.tue.nl>
       Eindhoven University of Technology
       Department of Mathematics and Computer Science
       Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

       Peter Orbaek <poe@daimi.aau.dk>
       Linux port and more options. Still maintains the code.

       Eric Rasmussen <ear@usfirst.org>
       Added -f option to display custom login messages on different terminals.

       Sat Nov 25 22:51:05 MET 1989


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